It looks like there are trains from Cambridge to Norwich every day. What day/time will you be traveling on?
I'll be leaving Sunday and need to arrive by 21:30.
train-arriveby train-day train-departure train-destination
train-arriveby train-day train-departure train-destination
train-arriveby train-day train-departure train-destination
train-arriveby train-day train-departure train-destination